Sudbury, MA November 2019 – DELO, one of the world’s leading manufacturers of industrial adhesives for automotive, consumer and industrial electronics applications, has partnered with Xaar, a world leader in the development of digital inkjet technology, to successfully jet materials at room temperatures with viscosities up to 250 mPa·s. Ideal for consumer and automotive optical applications, Xaar’s ultra high viscosity jetting capability is proving to be instrumental for DELO.

Inkjetting fluids with viscosities greater than 25 mPa·s

Most inkjet printheads are capable of jetting materials with a viscosity range of 10-25 mPa·s (10-25 cP). Xaar’s unique TF Technology (ink recirculation) allows DELO’s advanced optical fluids, with significantly higher viscosities, to be successfully jetted. In this application, fluids with a viscosity of 250 mPa·s at room temperature are heated to 43°C, reducing the viscosity to 63.5 mPa·s, and enabling them to be effectively ejected with Xaar’s printheads.

Having the capability to jet fluids with viscosities greater than 25 mPa·s allows manufacturers more design flexibility with optical elements in consumer electronics and automotive applications.  It also offers an alternative to imprint technology, which is predominantly used for selected applications like micro lenses.

Nano-imprint applications

For nano-imprint applications, inkjet-printing can also replace spin-coating, reducing material waste by up to 80 percent. Manufacturers can now use Xaar’s inkjet technology to create thin protective layers, reduce reflection losses or build light blocking structures or spacers. The capability is also proving valuable for 3D-printing to create single (micro) lenses and whole micro-lens arrays.

DELO has worked closely with Xaar to evaluate and develop this application using Xaar’s new 5-step process. The new program uses Xaar’s technical expertise and facilities, with dedicated laboratory space. The process helps with initial fluid evaluation and guidance through to sample production and application development. This enables customers to evaluate the technology with confidence. Continued support, technical advice and application improvements also form part of the process.

Ultra high viscosity and optical materials

Optical materials based on UV-curing polymers instead of glass or injection-molded plastics have become increasingly widespread in recent years. They are used as lenses for applications like flashlights, time-of-flight-sensors or diffractive optical elements (DOEs) for structured light emitters and miniature cameras.

DELO provides fast UV curing materials with excellent optical properties such as a matched refractive index, high transmission and non-yellowing. They are all solvent-free and provide adjusted mechanical functions and stability, as well as good adhesion and application on various substrates.

“Xaar’s ultra high viscosity capability enables us to jet optical materials with digitally controlled precision,” commented Karl Bitzer, head of product management at DELO. “We’ve been extremely impressed with the initial results which deliver both increased functionality of the fluid in the application and material savings and efficiencies.”

The precise placement of tiny droplets, a few picolitres in size, makes inkjet printing ideal for coating and protecting thin layers to achieve optical correction. It has proven to be a viable alternative to spin coating and other dispensing methods. It has also significantly reduced material waste up to 80 percent.

No nozzle blocking

Xaar’s unique recirculating TF Technology ensures unbeatable performance and excellent reliability without any nozzle blocking from large particles due to the fluid being kept in constant motion. It also offers increased functional capabilities for materials developers, including flexibility, low migration and increased gamut.

“While many printheads now incorporate recirculation, Xaar’s unique TF Technology is characterized by the recirculation being directly behind the nozzles at a very high flow rate, enabling the laydown of high-viscosity materials,” said Mike Seal, business development manager at Xaar. “This, together with our range of proven printheads, means we can provide advanced material suppliers like DELO with a new solution for their specific manufacturing applications.”